[Elecraft] New Crystals or Not

[Charles Greene]

Mike and All,

I have a question about the new xtals and the transmit bandwidth.  Do they 
do anything for it?  I really don't have any problems with receive 
sensitivity or receive bandpass aligned using Spectrogram; however, I don't 
use SSB much but I do use PSK31.  The transmit bandwidth varies a lot from 
LSB to USB on transmit.  Also, I have to reset the level control either on 
the computer or using an external pot when I go from a transmit signal of 
say 800 Hz to 2000 Hz.  It is particularity annoying as the K2 doesn't have 
a mike gain control to help in this regard.  For example, if I adjust the 
audio level for a power output of 5 watts at 800 Hz, it drops down to 
between 1 and 2 watts at 2000 Hz and is unusable above.  (You can't touch 
the power output control, as this introduces non-linearity which is fine 
for SSB but introduces unacceptable IMD for the digital modes).  Actually, 
the K2 has the best IMD of any transmitter I have seen, but the transmit 
bandpass drops off too much at the high end.

At 06:03 PM 10/28/2002 -0600, Mike McCoy wrote:
>I just completed the xtal replacement and I can pretty much echo Pauls
>observations. Not sure about the ripple but it's definately flatter,
>i.e.there is less slope across the passband (previously the filter 'fell
>off' about 6-8 db toward the high end). However, I now seem to have a -4
>to -5 db 'notch' about 400 hz wide smack in the middle though (now two big
>'ripple bumps' ? ;)  Even so it's no biggy... having an overall flatter
>response across the passband is a good thing.
>
>More importantly (at least in my case) the SSB passband is wider. The SSB
>passband with the xtals I received with my kit was only about 1400-1500 hz
>wide (@ -10 db) which made SSB sound umm.. 'pinched' (even after the SSB
>filter mod). After installing the new matched SSB xtals it's about 2.5Khz
>wide at 0 db and 1800-2K wide now @ -10 db. That improvement alone made it
>worth the effort for me.
>
>But that's not all... It's appears my problem of 'low audio' is gone. I can
>only presume it's due to an increase in receiver gain. Prior to the
>replacement I had to turn my audio gain pretty much fully clockwise (or use
>headphones) to hear anything. Now it's about 9 o'clock to achieve the same
>level.
>
>As a point of reference my original xtals were labled ECS 4.915-0195 (K2 sn
># 2602, ordered 4/15 and finished about 5/30)
>
>Bottom line, this retrofit certainly has my vote. While I felt the K2 was
>pretty darn decent before, I now feel like I have the K2 everyone has been
>raving about.


73, Chas, W1CG
K2 #462